This invention relates to the harnessing of the items and more particularly to the realization of efficient, lowcost, high strength harnessing devices which are easy to use.
Harnessing devices are widely used for the bundling of objects. Such devices are typically formed with a serrated strap that is fitted to an apertured head containing an internal pawl or locking tang that engages the serrations of the strap. Other harnessing devices are in the form of an apertured strap fitted to a buckle-like head, with a tongue that enters the apertures of the strap.
Harnessing devices with serrated straps have the disadvantage of being only as secure as their pawls. Where the items that are harnessed are heavy or are subjected to rough handling, the items often become accidentally released, for example, by failure of the pawls. Attempts have been made to strengthen serrated strap devices, but this has resulted in considerable complexity without achieving the desired end result of providing security against accidental release of the harnessed items. Similar objections apply to harnessing devices with buckle-like heads. In these devices, a tongue which enters the strap apertures rests against the head of the buckle near its opening and is deflected by the strap. The tongue is typically a cantilever attachment to the buckle-like head, which tends to be unduly stiff in the direction of forward thrust during harnessing, and insufficiently stiff in the direction of reverse thrust applied by the strap because of the harnessed items. In addition the tongue is exposed to external interferences that can cause an accidental release of the harnessed items.
Representative harnessing devices are disclosed in U.S. Pat. Nos. 515,747; 2,977,145; 3,030,131; 3,106,028; 3,127,648; 3,140,139; 3,189,961; 3,339,246; 3,368,247; 3,486,201; 3,457,598; 3,537,146; U.S. Pat. No. Re. 26,492; U.S. Pat. Nos. 3,542,321; 3,588,962; 3,598,442; 3,627,300; 3,654,669; 3,660,869; 3,731,347; 3,816,878; 3,840,256.
In order to avoid and overcome many of the difficulties associated with the foregoing kinds of harnessing devices, ladder straps and associated locking tangs have been developed of the kind disclosed in U.S. Pat. No. 3,766,608, which issued Oct. 23, 1973. The ladder strap device represents a significant improvement over the serrated strap and other harnessing devices. It can accomplish substantially the same functions as a serrated strap device at a considerably lower cost. The ladder strap can be produced with a significant saving in material and can be stretched to reorient its molecular structure and strengthen its constituents without strap distortion, as would occur if an attempt were made to stretch a serrated strap.
Notwithstanding its advantages, however, the ladder strap device requires a relatively massive locking tang or pawl in order to avoid failure from the reverse thrust of the items being harnessed. There are two kinds of pawl failure. The first is a loading failure by virtue of fracture of the pawl near its base. The second is "pawl pull". Here the reverse thrust produces a reverse rotation of the tang that is so great that the strap is released.
In addition the use of cross linked members to form the ladder portion of the strap requires care in molding to properly fill the mold and can also require special attention to the molding materials in order to achieve a satisfactory end product.
Accordingly, it is an object of the invention to provide for the secure harnessing of items. A related object is to achieve secure harnessing without the need for a complex harness configuration.
A further object of the invention is to reduce the strength characteristics needed for a locking pawl in a harnessing device of the ladder type. A related object is to achieve a less stringent locking pawl requirement while retaining the advantages of a ladder strap.
Another object of the invention is to reduce the material and molding requirements associated with the filling of molds and the production of harnessing devices. A related object is to reduce molding and material requirements in the manufacture of ladder strap harnessing devices.